GAITHERSBURG, Md., August 09, 2007 /PRNewswire-FirstCall/ --
Iomai Corporation today announced that interim results from a Phase
1 safety and immunogenicity trial of its patch-based vaccine for
travelers' diarrhea found that all subjects who received the
vaccine -- 19 elderly and 17 adult participants -- mounted an
immune response, demonstrating that even elderly subjects with
weaker immune systems respond to the vaccine.

The trial was designed to compare the number of elderly subjects
(65 and older) who seroconverted -- developed antibodies to the
vaccine's active ingredient -- with the number of adult
participants (aged 18 to 40) who seroconverted. Because the immune
system is often less powerful in older people, many vaccines do not
work as well in the elderly. However, all subjects who received the
Iomai patch, regardless of age, seroconverted with IgG antibodies.
Moreover, 18 of 19 elderly subjects and 15 of 17 adult subjects
also seroconverted with IgA antibodies. The study was conducted in
Belfast, Ireland, and subjects received two patches, 21 days apart,
containing "heat labile" toxin, or LT, and were followed for 42
days. No treatment- related serious adverse effects were
reported.

"The results of this trial further confirm that we can
effectively deliver the active ingredient in our patch-based
vaccine for travelers' diarrhea to adults of all ages, and based on
this data, the Iomai travelers' diarrhea vaccine could be expected
to extend coverage to this important at-risk segment of the
traveling population," said Gregory M. Glenn, M.D., senior vice
president and chief scientific officer of Iomai. "These results,
coupled with the remarkable findings from our field study that we
announced last week, provide additional evidence of the significant
potential for Iomai's transcutaneous immunization (TCI)
approach."

Iomai last week announced that a Phase 2 field trial of the
vaccine found that healthy adults who traveled to Guatemala and
Mexico and were vaccinated with the Iomai patch were 75 percent
less likely to suffer moderate or severe travelers' diarrhea. With
the high seroconversion rates in the elderly, the interim results
from this new study suggest that the protective effect of Iomai's
travelers' diarrhea vaccine may apply to all adults, not just young
adults. Iomai will look to confirm this in its Phase 3 trials for
its travelers' diarrhea vaccine, which the company intends to
launch in 2008.

The study was designed to evaluate the safety of the travelers'
diarrhea vaccine patch in the elderly and it met this primary
endpoint. The secondary objective included evaluation of
immunogenicity of the vaccine in the elderly compared with young
adults. Iomai plans to submit the study data from the trial for
publication as soon as possible.

ABOUT TRAVELERS' DIARRHEA

This year, approximately 55 million international travelers will
visit countries where bacteria that cause travelers' diarrhea are
endemic, particularly Africa, Asia and Latin America, and about 20
million of those travelers will develop travelers' diarrhea.

ETEC, the most common cause of travelers' diarrhea, represents
just under half of all cases of travelers' diarrhea for
international travelers to areas where ETEC is common. A recently
completed market study suggested that there is a large market for
an effective ETEC vaccine, potentially exceeding $500 million
annually. If approved, the Iomai vaccine would be the first vaccine
for travelers' diarrhea available in the United States.

ETEC's impact goes beyond travelers. The World Health
Organization estimates that children in the developing world suffer
210 million episodes of diarrhea caused by ETEC annually, causing
380,000 deaths each year.

ABOUT IOMAI CORPORATION

Iomai Corporation discovers and develops vaccines and immune
system stimulants, delivered via a novel, needle-free technology
called transcutaneous immunization (TCI). TCI, discovered by
researchers at the Walter Reed Army Institute of Research, taps
into the unique benefits of a major group of antigen-presenting
cells found in the outer layers of the skin (Langerhans cells) to
generate an enhanced immune response. Iomai is leveraging TCI to
enhance the efficacy of existing vaccines, develop new vaccines
that are viable only through transcutaneous administration and
expand the global vaccine market. Iomai currently has four product
candidates in development: three targeting influenza and pandemic
flu and one to prevent travelers' diarrhea.

Some matters discussed in this press release constitute
"forward-looking statements" that involve known and unknown risks
and uncertainties that could cause actual results to differ
materially from those expressed or implied by the forward-looking
statements. Such forward-looking statements include statements
about the predictability of the data from this trial in preventing
travelers' diarrhea in the elderly, timing and expectation for
Iomai commencing Phase 3 studies for this product candidate, and
bringing the product candidate to market; the potential size of the
market for an ETEC vaccine; the applicability of TCI technology to
other pathogens; and that, if approved, Iomai's vaccine would be
the first available in the U.S. Applicable risks and uncertainties
include, among others, that Iomai may not be able to enroll
sufficient numbers of patients in future clinical trials; that
future clinical trials may not replicate results seen in the trial
described in this press release; that Iomai may be unable to obtain
the regulatory approvals necessary to conduct additional clinical
trials or to market any product for travelers' diarrhea; that
estimates of market size overstate the number of travelers who
would use such a product, if it were approved; that competitors may
develop products that are safer, more effective, or more convenient
to use; and the risks identified under the heading "Factors That
May Impact Future Results" in Management's Discussion and Analysis
of Financial Condition and Results of Operations in Iomai's
Quarterly Report on Form 10-Q for the three months ended March 31,
2007, and filed with the Securities and Exchange Commission. While
Iomai believes that this product candidate is amenable to
self-administration, in the Phase 2 study described in this press
release, medical professionals administered the vaccine. Whether
any approved product would be self-administered would depend on
many factors, including the outcome of any studies the Company
conducts evaluating self-administration and the views of regulatory
agencies. Iomai cautions investors and others not to place undue
reliance on the forward-looking statements contained in this press
release. Iomai's business is subject to many risks.

The statements in this press release speak only as of the date
of this document, and Iomai undertakes no obligation to update or
revise the statements.